Keywords:

cerebral blood flow;

frontal hypometabolism;

frontal hypoperfusion;

oxygen metabolism;

positron emission tomography;

vascular dementia

Abstract

Vascular dementia is as common as Alzheimer's disease in Japan, although its importance has not been duly appreciated and its pathoetiology has not attracted proper attention. This article reviews the importance and pathophysiology of vascular dementia, presenting data obtained from our positron emission tomography (PET) study. Moreover, PET, ultrasonic quantitative blood flow measurements and magnetic resonance imaging findings on two ischemic conditions that may lead to vascular dementia are shown; chronic cerebral circulatory insufficiency (CCCI) and asymptomatic cerebral infarction. The review begins by describing the brief history, definition and classification of vascular dementia. Then, a detailed description of our PET study on patients with dementia as a result of cerebral infarction follows. Vascular dementia includes a large infarction in the territory of the right middle cerebral artery (LID), Binswanger-type infarction (BiD), multiple infarcts in the white matter and the basal ganglia (MID) and left anteromedial thalamic infarction (ThD). In addition, patients with a large infarction in the territory of the right middle cerebral artery (LIN), who did not have dementia, were used as a control group for LID. Healthy volunteers were also examined. This study demonstrates two types of dementia. Dementia observed in LID, MID and BiD reveals an overall reduction of blood flow and oxygen metabolism, which is accentuated in the frontal lobes. The second type, observed in ThD, shows a significant reduction in blood flow and oxygen metabolism in a relatively localized area in the left frontal lobe and the ipsilateral infarcted area. The etiological difference between the two types of dementia and the possible importance of frontal lobe hypoperfusion and hypometabolism are discussed. The review also examines the most important factor in dementia with multiple lacunae, concluding that widespread cerebral ischemia appears to be the most crucial factor. Finally, data on CCCI and asymptomatic cerebral infarction are described, which reveal that even these pre-stroke conditions have mild but significant hypoperfusion, concluding that preventive measures should be taken before ischemia advances.